Photons possess novel salient properties such as polarization, wavelength, coherence, speed, and spatial modes, which can play an important role for propagation and imaging in scattering media. Structured vector light spatial mode is an active research topic in various fields in classical and quantum entanglement applications. Photons can have unique vector properties which show that certain photons can be entangled locally and non-locally, separable and non-separable on wave front; can also posses spin angular momentum (SAM) and orbital angular momentum (OAM).
Due to inhomogeneous make up of tissue from particles and structure, biological tissues are highly scattering media. In this case, the wavelength plays a key role for biological media the scattering reduces as wavelength enters the NIR (650 nm to 950 nm) and in SWIR (1000 nm to 2500 nm). The optimum window in SWIR for deep imaging is the golden window (1600 to 1870 nm) in the brain.
Moreover, photon polarization plays an important role in tissues since it can affect the depth at which the beam travels. For example, it is known that circular polarized light goes deeper than linear polarized light in scattering media. Depending on scattering unit size, the polarization retains optical memory. A Laguerre-Gaussian beam (LG beam), which is a vortex beam, can carry different types of polarization (linear, circular, radial and azimuthal) along with a phase front characterized by an orbital angular momentum (OAM) of l value and spin angular momentum (SAM) S=+/−1. Light beams with spatially inhomogeneous profile of polarization are referred to as vector beams. The various spatial modes, such as the radial and azimuthal, have non-separable parts for circular polarization and OAM. The combination of polarization and spatial modes leads to special class of photons. These quasi particles are the basis proposed here as Majorana photons—where photons and antiphotons are the same.
The key characteristic of vector beams such as radial and azimuthal combines polarization and spatial modes, which are non-separable and are locally entangled. The focus of these beams have a longitudinal field. Moreover, the characteristic of non-separability in vector beams is of great interest not just in optical imaging but in optical communication and computers as well since its polarization degree of freedom and spatial mode are being explored to encode information. There are two special vector beams, radial and azimuthal; these two are a mixture of OAM and circular polarization; and are introduced here as Majorana modes and interaction in tissue for the first time. There is a search on for special quasi particles for storage and more stable for qubits that are less effected by interference and by the environment to reduce de-coherence effects and scattering.
Majorana can exist not only as fermions but also as bosons coincide of particle and antiparticle such as gravitons, photons and possible the neutrino, as they must be their own anti-particle and have opposite charges and same masses. Majorana only works for neutral particles. Charge and neutral particles have antiparticles; that is an electron with charge −e, so its antiparticle (the positron has charge of +e). These can not constitute a Majorana particle. However, the neutrino can fit, being a Majorana. Some have proposed bosons can be photons. Photons have no charge, the Majorana involves not only spin angular momentum but the vector sum of total angular momentum J, with OAM(l). Because of the transverse nature of electric (E) and magnetic (B) fields, the photon has zero rest mass. However, if special photons have a longitudinal field then the photon may have a small mass (Procar) on order of 10-49 gm. Majorana photons have both chiral twists. The key Majorana characteristic wave function feature is being its own anti-particle, where ψ=ψ*, being Hermitian. This Majorana as qubit of this type is topological which means its property remains almost the same regardless of the scattering exchange and the path taken in environment such as scattering. The Fourier transform of a pulse at ωo of duration τp in the time domain transforms mathematically into frequency domain signals centered at ωo and −ωo. Typically in an Optics course, one can drop the negative frequency −ωo as being physically not real. However, this is not totally correct. The negative frequencies of photons mean negative energy E=hν exactly what Dirac found when he completed solving relativistic quantum mechanics equations and found anti-electrons and anti-particles. Later, positron was found. Experimentally Ettore Majorara proposed a neutrino as being a particle being its own anti particle. Majorana neutrinos have the property that the neutrino and antineutrino could be distinguished only by chirality. If experiments observe a difference between the neutrino and antineutrino could simply be due to one particle with two possible chiralities. It is still not yet known whether neutrinos are Majorana or Dirac particles; photons do possess chirality in from of vector beams.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.